Superfund Research Program

Molecular Biomarkers for Assessing Testicular Toxicity

Project Leader: Kim Boekelheide
Grant Number: P42ES013660
Funding Period: 2009-2021

Project-Specific Links

Final Progress Reports

Year:   2020  2014 

Studies and Results

This past year, the researchers completed studies of co-exposure to low dose x-ray and 2,5-hexanedione, a combination of a physical agent and a chemical, both of which produce testicular injury in the rat (Specific Aims 1 and 2). The focus has been on understanding the detailed cellular and molecular processes that controlled the testicular injury response. Laser capture microdissection (LCM) was used to enrich for the toxicant-susceptible cell populations, extracting mRNA to be applied to apoptosis gene-related RT-PCR arrays. This research has led to the development of improved methods to investigate the molecular changes underlying mixed exposures, to inform further mechanistic studies, and to better inform risk assessment.

The major focus of this project is now on the development of sensitive and specific sperm biomarkers of testicular injury (Specific Aim 3). In the rat, model testicular toxicants are being used to identify toxicant-induced changes in mRNA content and DNA methylation in sperm, with the aim of developing candidate biomarkers to detect low levels of testicular injury manifested as molecular alterations in human sperm. A strong collaboration has developed with Hwang and Sigman in Brown University's Division of Urology, extending this work to the examination of sperm alterations in men exposed to various stresses, including alcohol and tobacco intake, obesity, and various pharmaceuticals. The ultimate goal is to extend this work to human-relevant monitoring of testicular effects of environmental exposures.

Significance

Three articles have been published this year describing co-exposure to low dose x-ray and 2,5-hexanedione, a combination of a physical agent and a chemical agent, both of which cause testicular injury. Laser capture microdissection was used to collect mRNA sensitive germ cell populations from the exposed rat testes to identify dose-dependent alterations in the apoptotic pathways activated by toxicant exposure. These data have provided detailed insight into mechanisms, dose-response, and interactions of combined exposures to testicular toxicants. The development of these low-dose co-exposure models of rat testicular toxicity have informed the experiments demonstrating that sperm molecular biomarkers have great potential for monitoring low-dose chronic exposures. Researchers continue to build on their now well-understood testicular injury models, with the goal of creating a biomarker panel of sperm mRNA transcripts and DNA methylation marks to evaluate their responsiveness to known reproductive toxicants in humans.